Electrodes for ventricular defibrillator



1965 E. M. BECKER ETAL 3,224,447

ELECTRODES FOR VENTRICULAR DEFIBRILLATOR Filed June 25, 1962 2Sheets-Sheet 2 ,m eox. T a u/ljack 0 M I I l APPRox. a M/LSEC. -l

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INVENTORS. EARL A4. BECKER MLL/AM C. STZ/C/(RATH BY ATTORA/EKS'.

United States Patent 3,224,447 ELECTRODES FOR VENTRICULAR DEFIBRILLATOREarl Matthew Becker and William Carl Stuckrath, Pittsburgh, Pa.,assignors to Mine Safety Appliances Company, a corporation ofPennsylvania Filed June 25, 1962, Ser. No. 204,949 4 Claims. (Cl.128-421) This invention relates generally to the electrodes used in aventricular defibrillator for shopping cardiac fibrillation by thedelivery of one or more pulses of high voltage electric current througha patients body in the region of the heart. More specifically, theinvention relates to electrodes that incorporate certain safety featuresfor the protection of the patient and those using the apparatus.

It is accordingly among the objects of this invention to provide a pairof electrodes for use in a cardiac defibrillator, in which theelectrodes will incorporate the following safety features, among others:(1) the electrodes will normally disconnect from the high voltage sourcethe electrode surfaces that are adapted to make contact with thepatients body; (2) when, and only when, both electrodes have beenpressed with a predetermined force against the patients body, will theelectrode contact surfaces be connected to the high voltage source; (3)where a pulse generator serves as the high voltage source, then when,and only when, both electrodes have been pressed with a still greaterforce against the patients body will the electrodes initiate theoperation of the pulse generator, i.e., a certain predetermined forcewill be necessary to connect the pulse generator to the contact surfacesof the electrodes and still greater force will be required to initiateoperation of the pulse generator to deliver a rapid series of electriccurrent pulses through the electrodes to the patients body.

Further objects will be apparent from the following description of theinvention, in connection with the attached drawings, in which:

FIG. 1 is a schematic wiring diagram of a defibrillator incorporatingthe present invention;

FIG. 2 is a sectional elevation of one of the electrodes, showingstructural details of the safety switches mounted therein; and

FIG. 3 is a representation of the wave shape of the current pulsesproduced by the discharge of two capacitors when connected in thecircuit of FIG. 1.

In accordance with this invention, which may be used in any type ofdefibrillator for delivering one or more pulses of electric current froma high voltage source or from a pulse generator through a pair ofelectrodes to a patients body, each electrode includes a conductingcontact surface, a stem mounted thereon, and a hollow insulated handleslidably receiving the stem. Means are provided for retaining the stemwithin the handle, but leaving it free for longitudinal reciprocationtherein; and spring means urge the stem in a direction out of thehandle. Inside the handle, a normally open first switch is adapted to beclosed only when the stem is pushed into the handle a predetermineddistance against the urging of the spring. When the first switch of eachelectrode is in its closed position, those switches connect the highvoltage source (for example an AC. transformer, one or more chargedcapacitors, etc.) to the electrodes. In one application of the invention(and the one described herein), where the electrodes are used with apulse generator (in the form of a sequence switch for separately andsuccessively discharging a plurality of capacitors), there isadditionally provided within each electrode handle a normally opensecond switch, which is adapted to be closed only when the stem ispushed into the handle a distance further than that required to closethe first switch. The second switches of the two electrodes areconnected together in series with a source of electric current and withelectromagnetic means, such as solenoid, for initiating the operation ofthe pulse generator. Accordingly, the pulse generator is first connectedto the electrodes and then its operation is initiated, in each casesolely in response to the application of a predetermined pressure on theelectrode handles with the contact surfaces of the electrodes restingagainst some relatively unyielding surface, such as the patients body.

Referring to the drawings, the general features of a defibrillator,including the electrical connections between its component parts, areshown schematically in FIG. 1. A source of electric current 1, which maybe either conventional volt AC. or batteries providing a lower voltage,such as 6 or 12-volt DC, is connected through a function switch 2 to atransformer-converter 3, either directly (as when the current source is115 volts AC.) or indirectly through a 6-volt converter 4 or a 12-voltconverter 6 (depending upon whether the source is 6 or 12 volts D.C.),which changes the 6 or 12 volt-s DC. to 115 volts A.C.

In transformer-converter 3, the 115 volt AC. input is changed to a 2,500volt DC, output, which is used to charge two high voltage capacitors C1and C2, connected in parallel to the voltage source through separatelimiting resistors R1 and R2, respectively, as shown in FIG. 1.Connected across the capacitors and their associated resistors is acharge light circuit that includes resistors 7, 8, and 9, and a neonglow discharge tube 11 with a capacitor 12 connected across it, as shownin FIG. 1. When the capacitors C1 and C2 are charged to somepredetermined voltage, tube 11 will blink. A shorting switch 13 inseries with a resistor 14 is also connected across capacitors C1 and C2,for discharging them otherwise than through the electrodes to bedescribed below.

Capacitors C1 and C2 are connected to a sequence switch generallydesignated by the numeral 21. The purpose of this switch is to dischargethe two capacitors C1 and C2 serially, so that they will deliver twoshort pulses of current with the second pulse following very quicklyafter the first one and having a reverse polarity (see FIG. 3). Switch21 is of the linear plunger type, with a handle 22 at one end of aninsulating rod 23 and armatures 24 and 26 at the other end of the rod.The two armatures are of conducting material, but they are insulatedfrom each other and separated by a circumferential groove 27. The switchis cocked by pulling the handleto the left in FIG. 1 until a locking pin28 drops into groove 27 and holds the armatures in their cockedpositions, as shown in broken lines in FIG. 1. A signal light 29connected to a low voltage source 31 through contacts 32 and 33 lightsup when those contacts are bridged by armature 24 to show that switch 21is in its cocked position. A spring motor 34 exerts a predeterminedaxial force on the plunger through a nylon cord 36, urging the armaturesto the right towards their uncocked position. In moving from theircocked to their uncooked positions, the armatures pass rapidly by andmomentarily engage a series of electrical contacts A, B, C, and D, andtheir diametrically opposed contacts A, B, C, and D. Contacts A and Dare connected to one side (here the positive side) of capacitors C1 andC2, respectively, while contacts B and C are connected to the othersides (here the negative sides) of both capacitors through a choke coil37. Contacts A and C are connected to electrode E1 and contacts B and Dto electrode E2.

The general circuit referred to above is described more fully andclaimed in the copending joint application of William P. Caywood andRobert S. Kush, Serial No.

20 1,948, filed of even date herewith and assigned to the same assignee.In addition, details of sequence switch 21 are more fully described andclaimed in the copending joint application of Earl M. Becker, one of theapplicants herein, and John I. Bridge, Serial No. 204,947, filed of evendate herewith and assigned to the same assignee. Contacts A and C areconnected to a first switch S1 in electrode El, while contacts B and Dare connected to a similar switch in electrode E2. Locking pin 28 isconnected through a bell crank 41 to the armature 42 of a solenoid 43.This solenoid is energized in a low voltage electrical circuit thatincludes, in series connection, a sec- 'ond' switch S2 in each ofthe'electrodes. It will be apparent'from FIG. 1 that electrodes E1 andE2 can receive pulses of current from capacitors C1 and C2 only after'(1) the first switches S1 associated with each electrode are closed and(2) the second switches S2 are also closed. In FIG. 2 are shown thestructural details done of the electrodes (say electrode E1) and of thefirst and second switches associated therewith, the other electrode E2having an identical structure. The electrode includes a metal contactsurface 51, which may be mounted on a plastic disc 52 of insulatingmaterial. A stem 53, also of insulating material, is secured to theplastic disc and is provided with a metal pin 54 extending axiallythrough it, the outer end of this pin making electrical contact with 7contact surface 51. The stem fits into a hollow insulating handle 56 andis held therein by a pin 57 extending through the wall of the handleinto a longitudinal slot 58 on the side of the stem. The stem, with itsattached electrode contact surface, is therefore free to move axially ofthe handle a predetermined distance, but cannot rotate relative to thehandle. A coil spring 59, compressed between a shoulder 61 on the insideof the handle and a shoulder 62 on the stem, urges the stem outwardsfrom the handle. The handle preferably has its lower end surrounded byan insulating hand guard, which may be a cupshaped rubber guard 63, asshown in FIG. 2, held between two insulating discs 64 and 66 mounted onthe end of the handle.

Inside the handle, the first electric switch S1 is adapted to be openedand closed by'inward axial movement of the stern relative to the handle.One of the many forms that this switch can take is shown in FIG.2,'where one element of the switch consists of spring contacts 67,mounted on the inner end of the stem and connected to the metal pin 54-and thus to the contacting surface 51; and the other switch element is aconducting sleeve 68, mounted inside the handle and connected through ahigh voltage conductor 69 in an electrical cable 70 to the appropriatesequence switch contacts, A and C, as shown in FIG. 1. In the normalposition of the electrode, with the stern extended outward to itsfullest extent under the compulsion of the coil spring, contacts 67 donot engage sleeve 68, and switch S1 is open. However, when the contactsurface of the electrode is placed against a patients body and thehandle pressed with suficient force to overcome the pressure of thespring, the stem will be pushed into the handle until contacts 67 engagesleeve 68 to close the first switch S1. Such closing connects theelectrode with the pulse generator, here represented by capacitors C1and C2 and sequence switch 21 with its associated contacts.

The second switch S2 is also mounted inside the electrode handle. It toomay take many forms and, in the example shown, includes two stationaryspring contacts 71, adapted to be bridged and electricallyinterconnected by a metal plunger 72 on the end of an insulating rod 73,which is supported on stem 53. The elements of this second switch,including the length of rod 73, are so dimensioned that switch S2 willclose only after the switch S1 has already closed. In other words, afterthe switch S1 is closed, the stern must be pushed further into thehandle in order to close the switch S2. Only upon the closing of thesecond switches S2 in both electrodes is a series circuit completedbetween a low voltage current source 74 and solenoid 43 for releasinglocking pin 28 to uncock sequence switch 21 to initiate the serialdischarge of capacitors C1 and C2.

When switch 21 is released from its cocked position, it moves quickly tothe right in FIG. 1. Armature 26 first bridges contacts A and A(connected to the positive side of capacitor C1), but no circuit isthereby completed. When armature 26 moves farther to the right to bridgecontacts B and B (connected to the negative sides of both capacitorsthrough choke coil 37), it is no longer in engagement with contacts Aand A; but armature 24 now bridges the latter contacts, completing acircuit that permits capacitor C1 to discharge through the twoelectrodes and the patients body, here represented by a resistance X. Amoment later, when the armatures bridge contacts B-B and CC, no currentflows through the electrodes. However, as soon as the armatures bridgecontacts CC and D-D, capacitor C2 discharges through the electrode andthe patients body, but in the reverse direction to the discharge ofcapacitor C1.

It is among the advantages of the present invention that it provides asafe, effective, and reliable means for arming the electrodes of a highvoltage defibrillator. While the invention can be used with any type ofdefibrillator, it is especially adapted for use with a defibrillatorthat includes a pulse generator, such as the capacitors and sequenceswitch described herein. In this particular defibrillator circuit, thecapacitors remain connected to the high voltage source even during theirdischarge, so that the contacts of the sequence switch would, except forthe safety features incorporated in the electrodes, connect thoseelectrodes to the high voltage source during the cocking of the sequenceswitch as well-as during its firing. However, the first switch means Slassociated with each of the electrodes effectively isolate thoseelectrodes from the high voltage source except when the electrodes areintentionally pressed with a predetermined pressure (for example, apressure on the order of ten pounds) against the patients body or someother relatively unyielding object. This feature gives assurance ofmaximum safety to operating personnel and to the patient, regardless ofthe position of the armatures in the sequence switch.

A further advantage of the electrode structure herein described is thatthe electrode contact surfaces 51, while axially movable with stems 53relative to handles 56, are not rotatable relative thereto, so that theusual contact jelly placed on those surfaces may be rubbed into the skinof the patient, by rotating the electrode handles, thereby assuring goodelectrical contact.

Another feature of the present invention is that the high voltage pulsegenerator, here represented by capacitors C1 and C2 and by sequenceswitch 21 with its associated electrical contacts, is first connected tothe electrodes before the operation of the pulse generator is initiated.The interval between the two events may be very short, but it isessential for the proper operation of the defibrillator that theelectrodes be already connected to the pulse generator when the latterdischarges its current pulses.

According to the provisions of the patent statutes, we have explainedthe principle of our invention and have illustrated and described whatwe now consider to represent its best embodiment. However, we desire tohave it understood that, within the scope of the appended claims, theinvention may be practiced otherwise than as specifically illustratedand described.

We claim:

1. In a cardiac defibrillator for delivering pulses of high voltageelectric current from a pulse generator through a pair of electrodes toa patients body, safety means for connecting the pulse generator to theelectrodes and for initiating operation of the pulse generator,comprising: separate first switch means associated with each electrodeand operable to connect each electrode to the pulse generator whentheelectrode is pressed with a-predetermined pressure against the body ofthe patient, electrically actuated triggering means for initiatingoperation of the pulse generator, separate second switch meansassociated with each electrode, an electrical series circuit including asource of electric current and both second switch means and thetriggering means, the second switch means being operable to actuate thetriggering means for initiating operation of the pulse generator solelyin response to a predetermined pressure of both electrodes against thepatients body in excess of the pressure required to operate the firstswitch means.

2. In a cardiac defibrillator for delivering pulses of high Voltageelectric current from a pulse generator through a pair of electrodes toa patients body, safety means for connecting the pulse generator to theelectrodes and for initiating operation of that generator, comprising:separate first switch means operable to connect each electrode to thepulse generator when the electrode is pressed with a predeterminedpressure against the body of the patient, electromagnetic means forinitiating operation of the pulse generator, separate second switchmeans associated with each electrode, an electrical series circuitincluding a source of electric current and both second switch means andthe electromagnetic means, the second switch means being operable toenergize the electromagnetic means in said circuit solely in response toa predetermined pressure of their associated electrode against thepatients body in excess of the pressure required to operate the firstswitch means.

3. In a cardiac defibrillator for delivering pulses of electric currentfrom a pulse generator through a pair of electrodes to a patients body,safety means for connecting the pulse generator to the electrodes andfor initiating operation of the generator, comprising: a stem mounted oneach electrode, a hollow handle slidably receiving the stem, meansretaining the stern within the handle for reciprocal longitudinalmovement therein, spring means urging the stern out of the handle,separate first switch means associated with each electrode and adaptedto be closed only when the stem is pushed into the handle apredetermined distance against the pressure of the spring means andoperable when closed to connect that electrode with the pulse generator,separate second switch means associated with each electrode and adaptedto be closed only when the stem is pushed into the handle apredetermined distance greater than the distance required to close thefirst switch means, electromagnetic means for initiating operation ofthe pulse generator, and a source of electric current connected in aseries circuit that includes the electromagnetic means and each of thesecond switch means for energizing the electromagnetic means only whenboth of the second switch means are closed.

4. Apparatus according to claim 3 that also includes means forpreventing rotation of each electrode relative to its handle.

. References Cited by the Examiner UNITED STATES PATENTS 1,471,85910/1923 Patton 128423 X 1,507,741 9/1924 Kirk 20016 2,106,687 1/1938Reetz 128418 X 2,534,043 12/1950 MacPhail 128423 2,864,371 12/1958Parodi 128-419 RICHARD A. GAUDET, Primary Examiner. JORDAN FRANKLIN,Examiner.

1. IN A CARDIAC DEFIBRILLATOR FOR DELIVERING PULSES OF HIGH VOLTAGEELECTRIC CURRENT FROM A PULSE GENERATOR THROUGH A PAIR OF ELECTRODES TOA PATIENT''S BODY, SAFETY MEANS FOR CONNECTING THE PULSE GENERATOR TOTHE ELECTRODES AND FOR INITIATING OPERATION OF THE PULSE GENERATOR,COMPRISING: SEPARATE FIRST SWITCH MEANS ASSOCIATED WITH EACH ELECTRODEAND OPERABLE TO CONNECT EACH ELECTRODE TO THE PULSE GENERATOR WHEN THEELECTRODE IS PRESSED WITH A PREDETERMINED PRESSURE AGAINST THE BODY OFTHE PATIENT, ELECTRICALLY ACTUATED TRIGGERING MEANS FOR INITIATINGOPERATION OF THE PULSE GENERATOR, SEPARATE SECOND SWITCH MEANSASSOCIATED WITH EACH ELECTRODE, AN ELECTRICAL SERIES CIRCUIT INCLUDING ASOURCE OF ELECTRICAL CURRENT AND BOTH SECOND SWITCH MEANS AND THETRIGGERING MEANS, THE SECOND SWITCH MEANS BEING OPERABLE TO ACTUATE THETRIGGERING MEANS FOR INITIATING OPERATION OF THE PULSE GENERATOR SOLELYIN RESPONSE TO A PREDETERMINED PRESSURE OF BOTH ELECTRODES AGAINST THEPATIENT''S BODY IN EXCESS OF THE PRESSURE REQUIRED TO OPERATE THE FIRSTSWITCH MEANS.